The female sex hormones estrone and estradiol are involved in many physiological processes. The formation of these steroids is regulated by a number of enzymes. The enzyme aromatase is the rate limiting enzyme in the non-reversible conversion of androgens (the hormones testosterone and androstenedione) to estrogens (the hormones estradiol and estrone). Materials such as aromatase inhibitors regulate or inhibit androgen to estrogen conversion, and thus have therapeutic utility in treating clinical conditions potentiated by the presence of estrogens. A further discussion of aromatase inhibitors may be found in U.S. Pat. No. 4,322,416.